Stator structure for synchronous electric motors



A. B. POOLE Sept. 5, 1939.

STATOR STRUCTURE FOR SYNCHRONOUS ELECTRIC MOTORS Filed May 13, 1938 2 Sheets-Sheet 1 5Cyl 12 Wye/74 0p ll/H A. B. POOLE Sept. 5, 1939.

STATOR STRUCTURE FOR SYNCHRONOUS ELECTRIC MOTORS Filed May 13, 1938 2 Sheets-Sheet 2 Patented Sept. 5, 1939 UNITED STATES PATENT OFFICE STATOR. STRUCTURE FOR SYNCHBONOUS ELECTRIC MOTORS Arthur B. Poole, Bristol, Conn, assignor to The E. Ingraham Company, Bristol,- Conn., a corporation of Connecticut Application May 13, 1938, Serial No. 207,670 16 Claims. (Cl. 172-278) This invention relates to an improvement in 'Fig. 8 is aperspective view of one of the bar-like stator-structures for synchronous electricsalient poles detached. motors, and is primarily concerned with stator- The stator-structure herein chosen for the structures for synchronous electric-motors of-the purpose of illustrating the present invention intype used in propelling clocks and other timecludes a cup-shaped pole-unit generally desig- 5 instruments. nated 'by the reference character it and a com- One of the objects of the present invention is plementary disk-like pole-unit generally desigto provide a superior stator-structure for syn nated by the reference character Ii, both of chronous electric-motors having a superior con= which are composed of suitable magnetic material 10 centration of magnetic flux immediately adjacent such, for instance, as silicon steel, soft iron or the 10 the rotor of such amotor. like. The cup-shaped pole-unit it has an end A further object is to provide a superior statorwall It! and an annular flange IB' The polestructure for synchronous electric-motors whereunit just referred to is of duplex character and in undue axial draft upon the rotor thereof may includes arelatively-deep outer cup-shaped mem- 10 be obviated. be! l2 and a relatively-shallow inner cup-shaped Still another object of the present invention member E3. The outer member l2 just referred is to provide a superior stator-structure whereby to d s an d-wall 2 and an annular flan e magnetic flux may be concentrated immediately 12'". The inner cup-shaped member i3 is tightly adjacent a rotor to thus increase the efhciency of fitted within the outer cup-shaped member I2 the synchronous motor-structure and at the same and, like the same, includes an end-wall l3 and 20 time avoid undue axial stresses upon suchrotor. an annular flange I3 which latter, however, is A still further object of the present invention slightly less in depth than the adjacent flange is to. provide a superior stator-structure for synl2 of the outer cup-shaped member i2, so that chronous electric-motors which will eiliciently its rear edge i3 provides a seat for the purpose act upon the rotor without imparting objeotionas will hereinafter appear. 25 able axial vibration thereto when the stator- The disk-like pole-unit ll comprises an outer structure is energized by alternating or other disk 15 and an inner disk l6 corresponding to sinuous current. each other in size and configuration and jointly With the above and other objects in view, as fitting within the open end of the outer cupwill appear to those skilled in the art from the shaped member IQ of the cup-shaped pole-unit so present disclosure, this invention includes all feal0 so that the inner disk It bears agains the outer tures in the said disclosure which are novel over edge I 3 of the inner cup-shaped member l3 of the prior art and which are not claimed in any the aforesaid cup-shaped pole-unit I0. For the separate application. purpose of retaining the disk-like pole-unit H in In the accompanying drawings, in which cerplace within the cup-shaped member l2 the 35 tain modes of carrying out the present invention flange I2 of the latter may be indented to proare shown for illustrative purposes: vide a suitable number of retaining-nibs such,

Fig. 1 is a front elevational view of a synfor instance, as the retaining-nib l'l shown in chronous electric motor embodying the stator- Figs. 3 and 4 of the accompanying drawings.

40 structure of the present invention; Projecting rearwardly from the end-wall ID- of 0 Fig. 2 is a view thereof in side elevation; the cup-shaped pole-unit ill in parallelism with Fig. 3 is a view showing the casing, the enerthe annular flange lo thereof, is an annularlygizZng-coil and the major portion of the cuparranged series ofbar iike salient poles l8 (six shaped pole-unit in section on the line 3-3 of more or less) formed of soft iron' or other suit- Fig. I; able magnetic material and arranged in (three 45 Fig. 4 is a central sectional view taken on the more or less) pairs around the axis of the strucline f 1; ture formed by the complemental pole-units l0 Fig. 5 is a sectional view taken on the line 5-5 and II, so that the individual salient poles of each pair thereof are more closely spaced to- Fig. 6 is a perspective view partly in section gether than are the several pairs with respect to 50 of the cup-shaped pole-unit together with its each adjacent pair. In a similar manner, an shading-disk and annular series of salient poles; annular series of bar-like salient poles, each gen- Fig. 7 is a perspective view of the disk-like erally designated by the reference character I 9, pole-unit together with its shading-disk and anextend forwardly from the disk-like poleunlt I I. nular series of salient poles; and The salient poles I 9 are arranged in a manner corresponding to that with the salientpoles I8 of the disk-like pole-unit I0, so that a pair of salient poles of one of the pole-units fits into a relatively-wide gap between the respective pairs of salient poles of the other unit. The result of the spacing of the salient poles just above described is such that when the two pole-units I9 and I I are assembled, the salient poles of like polarity are spacedrelatively widely apart, while the salient poles of unlike polarity are spaced in very close proximity to each other, as will be apparent by reference to Fig. 5 in particular.

For the purpose of economy in manufacture, the salient poles I8 and I9 above referred to, all correspond to each other in size and form so as to be interchangeable one for the other.

Each of the salient poles I8 and I9 includes a body-portion of substantially rectangular form in cross-section though having a slightly-concaved inner face 2I and a slightly-convexed outer face 22,.each of such curvature as to extend substantially concentrically with respect to the axis of the pole-units I6 and II. Each of the salient poles I8 and I9 is formed at one end with acylindrical shank 23 which extends with a drivefit into a suitable perforation 24, an appropriately-spaced annular series of which is formed in the end-wall II] of the cup-shaped pole-unit I0- and in the disk-like pole-unit II. Preferably and as shown in Figs. 3 and 4, the ends of the shanks 23 of each salient pole I8 and I9 are headed over as at 25 against the outer face of the immediately-adjacent portion of the particular pole-unit I0 or II in which mountedas described.

At the extreme end of each salient pole I8 and I9 opposite its shank 23, there is provided a stabilizing-tench 26 for the purpose as will hereinafter appear. Each salient pole I8 and I9 is formed intermediate its rectangular body-portion 20 and its stabilizing-tench 26 with a cylindrically-contoured flux-restricting neck or portion 21 which as will more fully hereinafter appear, serves to restrict the flow of magnetic flux and cause the latter to flow mainly from the bodyportion 20 to a rotor-unit. 1

As thus constructed and arranged the statorstructure includes two spaced-apart magneticportions (the end wall Ill and the pole-unit II) from each of which salient poles project toward the other magnetic-portion.

Positioned against the inner face of the endwall ll) of the cup-shaped pole-unit I0 is a shad-- ing-disk 28 composed of copper or other suitable high-electro-conductive material and formed with an annular series of substantially-rectangular perforations 29, each of which is shaped and located so as to snugly fit over the base of the body-portion 20 of one of the salient poles I8 of the pole-unit ID, to thus supplement the action of the shank 23 of a given salient pole in holding the same in properly-oriented position. Each alternate one of the polygonal perforations 29 is intersected by a radial slot 39 which thus interrupts the flow of induced current in the portion of the shading-disk 28 around the particular one of the salient poles I8 which happens to extend through one of the said intersected perforations 29. The remaining three perforations 29 are not intersected by slots, as will be seen by reference to Fig. 6, and'the material of the shading-disk 28 which surrounds them is electrically continuous and provides a complete electrical path for the flow of induced current around the particu ar described in connection the particular salient pole is three salient poles I8 projecting through the said non-intersected perforations 29.

From the foregoing it will be seen that each alternate one of the salient poles I8 is shaded, so

to speak, by the shading-disk 28 so that the magnetic flux in these particular salient poles will lag with respect to the magnetic flux in the remaining three unshaded salient poles I8 so as to produce a rotating-field efiect.

Positioned against the inner face of the disklike pole-unit II is a shading-disk 3I corresponding in its main characteristics and functions to the shading-disk 28 just above described and like the same, provided with six (more or less) substantially-rectangular perforations 32, each of which snugly fits over the base of the substantially-rectangular body-portion 20 of one of the salient poles I9 of the disk-like pole-unit I I. The material of the shading-disk 3I (copper or the like) around three of the six perforations 32 is electrically continuous so as to provide for the flow of induced currents around the particular three salient poles I9 respectively extending therethrough. The remaining three perforations 32 in the shading-disk 3| are, as is particularly well shown in Fig. 7, intersected by radial slots 33 extending through the outer edge of the disk 3I and serving to interrupt the flow of induced C111.

rent around the particular three salient poles I9 extending through these latter three intersected perforations 32.

From the foregoing it will be seen that three of the salient poles I9 of the disk-like pole-unitI I are shaded by the shading-disk 3I so that the magnetic flux flowing therethrough will lag with respect to .the magnetic flux flowing through the remaining three salient poles I9 which extend through the'particular perforations 32 which are intersected by the radial slots 33 above described. This shading of alternate salient poles I9 produces, a rotating-field efi'ect similar to that described in connection with the salient poles I8 of the pole-unit; I0 and having a similar direction of rotation so as to exert a turning torque upon a rotor-unit to be later described.

The stabilizing-tench 26 at the otherwise free end of each of the salient poles I8 is preferably slightly tapered for being forced witha drive-fit into a correspondingly-located perforation 34 (one of six perforations) in the shading-disk 3I of the disk-like pole-unit II. Thus, each of the respective opposite ends of each ofthe bar-like salient poles I8 is firmly held against displacement or vibration'under the influence of pulsat-- ing magnetic flux.

In a similar manner, the stabilizing-tenons 26 of the salient poles I9 of the disk-like pole-unit I I are each preferably slightly tapered for being forced with a drive-fit into an aligned perforation (one of six perforations) 35 in the shadingdisk 28 of the cup-shaped pole-unit I0, so that the. otherwise-free ends of the said salient poles I9 are also firmly held against displacement or vibration.

Surrounding the salient poles I8 and I9 which as before explained, are arranged in an annular series, is an energizing-coil 36 having two insulated leads 3'! and 38 which project through one of the three radial slots 33 in the adjacent shadnated by the reference character 4|. The said rotor-unit is of composite character and includes a rotor-hub 42 which is preferably formed of nonmagnetic material such, for instance, as brass, and upon which is rigidly mounted a pair of corresponding but oppositely-facing cup-shaped rotor-elements 4343. The said rotor-elements 43-43 are preferably formed of hard steel or other suitable permanent-magnet material and are spaced from each other by a salient-poled rotor-element 44 which is preferably formed of soft iron or other non-permanent magnetic material. The said cup-shaped rotor-elements 4343 preferably have smooth outer peripheries so as not to provide marked geometrically-salient poles but which, owing to their permanent magnetic character are adapted to receive magnetic spottings so to speak, which will be impressed upon them by the adjacent salient poles of the stator-structure, in accordance with well-understood principles in the art.

The rotor-hub 42 is provided at its forward end with a sleeve-like bearing-portion 45 which rotates upon the adjacent surface of a center-arbor 46 which in turn is journaled at its forward end in a bearing-opening 47 in the adjacent shadingdisk 28. The rear portion of the center-arbor 46 bears in a bearing-opening 48 formed in a bearing-plate 49 which latter is located in spaced relationship rearwardly of the disk-like poleunit before referred to. The said bearingplate 49 is supported in spaced relationship as just described by means of a suitable number of pillars 50 as is indicated in Figs. 3 and 4.

The rear end of the rotor-hub 42 is formed with a rearwardly-extending sleeve-l ke portion having an axial passage 52 extending there.- through as well as through the main portion of the adjacent rotor-hub 42 proper as is shown in Fig. 4-. The axial passage 52 just referred to is considerably larger in diameter than the diameter of the center-arbor 46 which extends therethrough, and receives at its rear end with a drivefit the forward end of a drive-pinion 53 which bears with freedom for rotation upon the centerarbor 46 and permits oil to enter the interior of the rotor-hub by way of the gaps between its gear-teeth.

As thus constructed and arranged, the rotorunit rigidly carries the drive-p nion 53 and the latter acts through a reductlon-gear-train gen- ,erally designated by the reference character 54 to 7 drive a power-output shaft 55 from which may be driven a clock-mechanism or the like. The particular character of the reduction-gear-train 54 is not here involved and it need not be described in detail other than to say, as above, that it serves to operatively interconnect the drive-pinion 53 of the rotor-unit 4| with the power-output shaft 55.

In the structure shown, all of the parts above described, with the exception of the forward end of the power-output shaft 55, are housed within a two-part housing generally designated by the reference character 56, and which may if desired be made of relatively-light sheet-steel or other suitable material of an oil-tight nature. The said housing 56 includes a relatively-deep cupshaped housing-member generally designated by the reference character 51 and which has a substantially-fiat rear end-wall 58 and a deep annular flange 59. The open forward end of the cupshaped housing-member 51 is closed by a flanged housing-cap generally designated by the reference character 60 and which includes a substantially-flat end-wall 6| and a relatively-shallow rearwardly-projecting annular flange 62 which fits over the exterior of the adjacent open end of the flange 59 of the main housing-member 51 and is preferably cemented, soldered or otherwise sealed in an oil-tight manner to the said housing-member 51.

The leads 31 and 38 of the energizing-coil 36 may be led outwardly from the interior to the exterior of the housing 56 in any suitable manner, such, for instance, as through terminal-fittings 63 and 64 and may be exteriorly connected to supply-wires 65 and 66, as indicated in Figs. 1 and 2 in particular.

As before noted, the present invention is concerned mainly with the stator-structure which comprises in the main, the cup-shaped pole-unit l0, the disk-like pole-unit H, the salient poles l8 and I9 projecting therefrom.

By providing each of the salient poles l8 and IS with a reduced portion or neck, such as 21, the magnetic flux flowing from a given one of the said salient poles to the rotor is restricted at this point and compelled to mainly flow directly to the rotor-unit 4| from the relatively-large bodyportions 20 of the said salient poles. It will be noted that the body-portions 20 have inner faces of much greater width or extent in the direction of rotation of the rotor-unit 4| than have the said flux-restricting necks 21.

Furthermore, by locating the flux-restricting necks 21 at the outer end of each salient pole, rather than at the inner end thereof, the desired efiect is achieved without materially affecting the flow of magnetic flux into a given salient pole from the particular pole-unit of which it forms a feature.

As will be seen most clearly by reference to Figs. 3 and 4 of the accompanying drawings, the provision of the salient poles I8 and IS with the flux-restricting necks 21 or their equivalent, the magnetic flux is concentrated mainly upon the periphery of the rotor-unit 4| without exerting such degree of axial draft upon the same as would cause the rotor-unit to materially shift or vibrate axially to thereby possibly cause the faulty operation of the motor and produce objectionable hum due to the constantly-changing polarities of the respective pole-units I0 and H and their respective salient poles IB and IS.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I claim:

1. A stator-structure for cooperation with the rotor of a synchronous electric motor, including in combination: a first magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a plurality of salient poles projecting laterally from the said first magneticportion toward the .said second magnetic-portion; a plurality of salient poles projecting lateraly in the opposite direction from the said second magnetic-portion toward the said first magneticp-: rtion; and an energizing-coil for magnetizing the two said magnetic-portions and the oppositely-projecting salient poles; each of the said salient poles of each of the said magneticportions comprising a portion of relatively-large cross-sectional area and a portion of materiallylesser' crosssectional area; the portions of-the said materially-lesser cross-sectional area being arranged in the oppositely-projecting salient poles 'for positioning remotely with respect to the rotor, and the portions of the said relatively-large cross-sectional area being located in the said salient poles for positioning in corresponding proximate relation to the rotor, whereby the latter portions of the salient poles provide in the magnetic-field of the stator-structure, a zone of relatively-high magnetic flux arranged to be traversed by the rotor.

2. A stator-structure for cooperation with the rotor of a synchronous electric motor, including in combination: a first magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a plurality of salient poles projecting laterally from the said first magnetic-portion toward the said second magnetic-portion; a plurality of salient poles projecting laterally in the opposite direction from the said second magneticportion toward the said first magnetic-portion;

and an energizing-coil for magnetizing the two said magnetic-portions and the oppositely projecting salient poles; each of the saidsalientpoles of each of the said'magnetic-portions com-. prising a portion of relatively-large cross-sectional area and -a portion of materially-lesser cross-sectional area located at the outer end of its projecting end; the portions of the said materially-lesser cross-sectional area being arranged in the oppositely-projecting salient poles for positioning remotely with respect to the rotor, and

the portions of the said relatively-large crosssectional area being located in the said salient poles for positioning in corresponding proximate relation to the rotor, whereby the latter portions of the salient poles provide in the magnetic-field of the stator-structure, a zone of relatively-high magnetic fiux arranged to be traversed by the rotor.

3. A stator-structure for cooperation with the rotor of a synchronous electric motor, including in combination: a first magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a plurality of salient poles projecting laterally from the said first magneticportion toward the said second magnetic-pontion; a plurality of salient poles projecting laterally in the opposite direction from the said second magnetic-portion toward the said first magnetic-portion; and an energizing-coil for magnetizing the two said magnetic-portions and the oppositely-projecting salient poles; said salient poles of each of the said magneticportions comprising a portion having an inner facial width of relatively-great extent and each of the said salient poles also having a portion of materially-lesser inner facial'extent; the portions of the said materially-lesser inner facial width being arranged in the oppositely-projecting salient poles for positioning remotely with respect to each 'of the rotor of a synchronous electric motor, including in combination: a first magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a plurality of salient poles projecting laterally from the said first magneticportion toward the said second magnetic-portion; a plurality of salient poles projecting laterally in theopposite direction from the said second magnetic-portion toward the said first magnetic-portion; and an energizing-coil =for magnetizing the two said magnetic-portions projecting salient poles; each of the said salient poles of each of the said magnetic-portions comprising a portion having an inner facial width of relatively-great extent and each of the said salient poles also having a portion of materiallylesser inner facial extent located at its projecting end; the portions of the said materially-lesser inner facial width being arranged in the oppositely-projecting salient poles for positioning remotely with respect to the rotor, and the portions of the said relatively-great inner facial width being located in the said salient poles for positioning in corresponding proximate relation to the rotor, whereby the latter portions of the salient poles provide in the magnetic-field of the stator-structure, a zone of relatively-high magnetic flux arranged to be traversed by the rotor.

5. A stator-structure for synchronous electric motors, including in combination: a first magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a plurality of salient poles projecting from the said flrst-nnagnetic-portion toward the said second magneticrportion; a plurality of salient poles projecting from the said secondmagnetic-portion toward the said first magnetic-portion; and an energizing-coil for magnetizing the two said magnetic-portions and the salient poles projecting therefrom; each of the said salient poles of each of the said magnetic-portions being provided with a body-portion of substantially-rectangular form in cross-section and a flux-restricting portion of substantially circular form in cross-section and of materially-lesser cross-sectional area than the said body-portion.

6. A stator structure for synchronous electric first magnetic-portion toward the said second magnetic-portion; a plurality of salient poles promagnetic-portion 4 jecting from the said second toward the said first magnetic-portion; and an energizing-coil for magnetizing the two said magnetic-portions and the salient poles projecting therefrom; each of the said salient poles of each of the said magnetic-portions being provided with a body-portion of. substantially-rectangular form in cross-section and a flux-restricting portion of substantially-circular form in cross-section and of materially-lesser cross-sectional area than the said body-portion and located at a point beyond the said body-portion remote from the magnetic-portion from which the salient pole projects.

'7. A stator-structure for synchronous electric motors, including in combination: a fir t magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a pluand the oppositely rality of salient poles projecting from the said first magnetic-portion toward the said second magnetic-portion; a plurality of salient poles projecting from the said second magnetic-portion toward the said first magnetic-portion; and an energizing-coil for magnetizing the two said magnetic-portions and the salient poles projecting therefrom; each of the said salient poles each of the said magnetic-portions being provid d with a body-portion having a concaved inner face of relatively-great width and each of the said salient poles also having a flux-restricting portion having a convex inner face.

8. A stator-structure for synchronous electricmotors, including in combination: a first magnetic-portion; a second magnetic-portion spaced from the said first magnetic-portion and extending in substantial parallelism therewith; a plurality of salient poles projecting from the said first magnetic-portion toward the said second magnetic-portion; a plurality of salient poles prolecting from the said second magnetic-portion toward the said first magnetic-portion; and an energizing-coil for magnetizing the two said magnetic-portions and the salient poles projecting therefrom; each of the said salient poles of each of the said magnetic-portions being provided with a body-portion having a concave inner face of relatively-great width and each of the said salientpoles also having a fiux-restricting-portion having a convex inner face which is located at a point on the salient pole on the side of the said body-portion remote from the magnetic-portion by which the salient pole is carried.

9. A stator-structure for cooperation with the rotor of a synchronous electric-motor, including in combination: a cup-shaped pole-unit having an end-wal1 and a flange; a disk-like pole-unit substantially closing the open end of the said cupshaped pole-unit; a plurality of salient poles projecting laterally from the end-wall of the said cup-shaped pole unit toward the said disk-like pole-unit; a plurality of salient poles projecting laterally in the opposite direction from the said disk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and a ring-like energizing-coil located within the said cup-shaped pole-unit intermediate the flange thereof and the oppositely-projecting salient poles; each of the said salient poles of each of the said pole-units comprising a portion of relatively-large crosssectional area and a portion of materially-lesser cross-sectional area; the portions of the said materially-lesser cross-sectional area being arranged in the oppositely-projecting salient poles for positioning remotely with respect to the rotor, and the portions of the said relatively large crosssectional area being located in the said salient poles for positioning in correspondlng proximate relation to the rotor, whereby the latter portions of the salient poles providein the magnetic-field of the-statorstructure, a zone of relatively-high magnetic flux arranged to be traversed by the rotor.

10. A stator-structure for cooperation with the rotor of a synchronous electric-motor, including in combination: a cup-shaped pole-unit having an end-wall and a flange; a disk like pole-unit substantially closing the open end of the said cupshaped pole-unit; a plurality of salient poles projecting laterally from the end-wall of the said cup-shaped pole-unit toward the said disk-like pole-unit; a plurality of salient poles projecting laterally in the opposite direction from the said disk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and a ring-like energizing-coil located within the said cup-shaped pole-unit intermediate the flange thereof and the oppositely-projecting salient poles; each of the said salient poles of each of the said pole-units comprising a portion of relatively-large crosssectional area and a portion of materially-lesser cross-sectional area located at its projecting end; the portions of the said materially-lesser crosssectional area being arranged in the oppositelywrth respect to the rotor, and the portions of the said relatively-large cross-sectional area being located in the said salient poles for positioning in corresponding proximate relation to the rotor, whereby the latter portions of the salient poles provide in the magnetic-field of the stator-structure, a zone of relatively-high magnetic flux arranged to be traversed by the rotor.

11. A stator-structure for cooperation with the rotor of a synchronous electric-motor, including in combination: a cup-shaped pole-unit having an end-wall and a flange; a disk-like pole-unit substantially closing the open end of the said cup-shaped pole-unit; a plurality of salient poles projecting laterally from the end-wall of the said cup-shaped pole-unit toward the said disk-like pole-unit; a plurality of salient poles projecting laterally in the opposite direction from the said disk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and a ring-like energizing-coil located within the said cup-shaped pole-unit intermediate the flange thereof and the oppositely projecting salient poles; each of the said salient poles of each of the said pole-units comprising a portion having an inner facial width of relatively-great extent and each of the said ranged in the oppositely-projecting salient poles for positioning remotely with respect to the rotor, said relatively-great in her facial width being located in the said salient projecting laterally from the end-wall of the said cup-shaped pole-unit toward the said disklike pole-unit; a plurality of salient poles projecting laterally in the opposite direction from the said disk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and a ringlike energizing-coil located within the said cupshaped pole-unit intermediate the flange thereprojecting salient poles; each of the said salient poles of each of the said pole-units comprising a portion having an inner facial width of relatively-great extent and each of the said salient poles also having a portion of materially-lesser inner facial extent than the facial extent of the said body-portion located at its projecting end; the portions of the said materially-lesser inner facial width being arranged in the oppositely-projecting salient poles for positioning remotely with respect to the rotor,

and the portions of the, said relatively-great inner .facial width being located in the said salient poles for positioning in corresponding proximate relation to the rotor, whereby the latter portions of the salient poles provide in the magnetic-field of the stator-structure, a zone of relatively-high be traversed by the plurality of salient poles projecting from the said the end-wall of the disk-like pole-unit toward said cup-shaped pole-unit; and aring-like energizing-coil located within the said cup-shaped pole-unit intermediate the flange thereof and the salient poles projecting therefrom; each of the said salient poles of each of the said pole-units being provided with a body-portion of substantially-rectangular form in cross-section and a flux-restricting portion of substantially-circular form in cross-sectional area than the said body-portion. 14. A stator-structure for synchronous electrio-motors, including in combination: a cupshaped pole-unit having an end-wall and a flange; tially closing the open end of. the said cupshaped pole-unit; a plurality of salient poles projecting from the end-wall of the .said cupshaped pole-unit toward the said disk-like poleunit; a plurality of salient poles projecting from the 'saidcdisk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and a ring-like energizing-coil located within the said cupshaped pole-unit intermediate the flange thereof and the salient poles projecting therefrom; each of the said salient poles of each of the said poleunits being provided with a body-portion of substantially-rectangular form in cross-section and a flux-restricting portion of substantially-circular form in'cross-section and of materiallycross-section and of materially-lesser a disk-like magnetic-portion substan-.

lesser cross-sectional area than the said bodyportion and located at a point beyond the said body-portion remote from the pole-unit from which the salient pole projects. A

15. A stator-structure for synchronous electrio-motors, including in combination: a cupshaped pole-unit having. an end-wall and a flange; a disk-like magnetic-portion substanplurality of salient poles projecting from the said disk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and a ring-like energizing-coil located within the said cup-shaped pole-unit intermediate the flange thereof and the salient poles proj said salient poles of each of the said pole-units being provided with a body-portion and having a concaved inner face of relatively-great width and each of the said salient poles also having a fluxrestricting portion having a convex inner face.

.tially closing the open end of the said cup-shaped ectingj therefrom; each of the- 16. A stator-structure for synchronous electrio-motors, including in combination: a cupshaped pole-unit having an end-wall and a flange; adisk-like. magnetic-portion substantially closing the open end of the said cup-shaped pole-unit; a plurality of salient poles projecting from the, end-wall of the said cup-shaped poleunit toward the said disk-like pole-unit; a plurality of.salient poles projecting from the said disk-like pole-unit toward the end-wall of the said cup-shaped pole-unit; and'a ring-like energizing-coilr located within .the said cup-shaped pole-unit intermediate the flange thereof and the salientpolesprojecting therefrom; each of thesaid salient poles of each of the said pole-units being provided with a body-portion having a concaved inner face of relatively-great width and each of the said salient poles also having a flux-restricting portion having a convex inner face which is located at a point on the salient pole on the side of the said body-portion remote from the poleunit by which the salient pole is carried.

ARTH R B. POOLE. 

